Chromium Corundum Furnace Lining for High-Fluorine Waste Ashing
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Solution Overview
Problem
Existing methods for incinerating waste with high fluorine and precious metal content, such as those described in EP 2 700 726 A1, are limited by a maximum fluorine content of 5% by weight, making them ineffective for materials with higher fluorine and precious metal concentrations.
Innovation Solution
A process using a chamber furnace with a chromium corundum lining comprising ≥80% alpha-Al2O3, 1 to 20% Cr2O3, and 0 to 5% SiO2, allowing for the incineration of waste with fluorine content ranging from >5 to 70% by weight and precious metal content from 0.1 to 30% by weight, enabling continuous operation and efficient ash formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a refractory insulating lining with high aluminum oxide content (≥85 wt.%) is used in the chamber furnace, then the lining is resistant to hydrofluoric acid attack, but the maximum fluorine content of waste that can be incinerated is limited to 5 wt.%
Solution Approach 1:
The invention changes the chemical composition parameters of the refractory lining by adding chromium oxide (Cr2O3) in amounts of 1-20 wt.% to the aluminum oxide-based material. This compositional modification transforms the lining's properties, enabling it to withstand hydrofluoric acid attack even when processing waste with fluorine content up to 70 wt.%, thereby resolving the contradiction between acid resistance and processable waste concentration.
2Productivity
If the fluorine content of waste is increased above 5 wt.% to improve resource utilization, then more valuable materials can be processed, but the existing refractory lining becomes attacked and damaged by hydrofluoric acid
Solution Approach 1:
The invention creates a composite refractory material by combining aluminum oxide (≥80 wt.%) with chromium oxide (1-20 wt.%) and silicon dioxide (0-5 wt.%). This composite structure synergistically provides both the chemical resistance needed to withstand high fluorine content waste and the structural integrity required for durable operation, enabling processing of waste with up to 70 wt.% fluorine without lining damage.
3Reliability
If a chromium corundum lining is used to process high fluorine content waste (>5 to 70 wt.%), then the lining maintains durability and resistance, but the composition becomes more complex compared to simple aluminum oxide linings
Solution Approach 1:
The invention applies local quality by concentrating the chromium oxide addition specifically in the refractory lining material where chemical resistance is most critical, while maintaining the bulk aluminum oxide structure for structural support. This targeted compositional modification provides enhanced durability against hydrofluoric acid attack without unnecessarily complicating the overall lining system, achieving reliable performance in high fluorine environments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables the effective incineration and enrichment of precious metals in waste with high fluorine content, allowing for continuous operation over extended periods without lining replacement, with rapid temperature changes and high processing capacity.
Implementation Method 1
the furnace chamber of the chamber furnace is lined with a chromium corundum material comprising ≥80 wt.% alpha-Al2O3, 1 to 20 wt.% Cr2O3 and 0 to 5 wt.% SiO2
Implementation Method 2
incinerating the waste
Implementation Method 3
Incineration of such waste produces, among other substances, hydrogen fluoride or hydrofluoric acid
Data Source
AI summary
A process for ashing fluorine- and precious metal-containing waste in a chamber furnace, wherein the fluorine content of the waste is in the range of >5 to 70 wt.% and the precious metal content of the waste is in the range of 0.1 to 30 wt.% and wherein the furnace chamber of the chamber furnace is lined with a chromium corundum material comprising ≥80 wt.% alpha-Al2O3, 1 to 20 wt.% Cr2O3 and 0 to 5 wt.% SiO2.